This invention relates generally to dampers and, more particularly, to vibration mounts of the elastomeric type.
Resilient mounting means are often used to isolate or dampen the vibration of operating machinery from other associated parts of machinery. Such is the case in an aircraft engine apparatus wherein it is desirable, for example, to mount an oil tank on the engine which is susceptible to vibration and which without isolation will produce fatigue cracks in the sheet metal skin of the tank.
One means of isolating such vibrational movement is to fasten an elastomeric material between the vibrating element and the element which is mounted thereto. Such an arrangement will provide adequate damping when the two elements are moving relatively toward each other (axially), since the elastic material will be in compression. However, when the two elements are moving away from each other there will be no damping provided. Further, when the two elements are moving transversely to each other (radially), then there is a damping action, but it tends to create a shear force on the elastic material which in time will finally cut and tear the material and render it useless. Various methods have been devised to provide compressive elastomeric damping for either axial direction, but in all such devices there is no provision for preventing the shear forces which occur from the radial vibrations.
It is, therefore, an object of the present invention to provide an isolation mount which dampens relative movement in either the axial or radial directions.
Another object of the present invention is the provision for an isolation damper which is effective in damping radial forces without attendant shear forces being imposed on the elastomeric medium.
Yet another object of the present invention is the provision for an isolation mount which is effective in use and economical and practical in design.
Another objective of the present invention is to provide a mount which limits deflection in both the radial and axial directions.
These objects and other features and advantages become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.
Briefly, in accordance with one aspect of the invention, a toroidal casing which is adapted for attachment to an element for which damping is desired, is provided with a pair of axially spaced, elastomeric O-rings. A plate, which is attachable to the vibrating engine, extends radially inward through the casing wall and between the O-rings to a point surrounding but not touching the central core of the toroidal casing. The plate then flanges in opposite directions toward the ends of the toroidal casing to entrap the elastomeric O-rings between the flanges and the respective oppositely disposed casing walls. When the plate moves axially with respect to the casing, one of the two elastomeric O-rings is compressed between the plate and the casing end wall, while the other elastomeric O-ring is not affected. When the plate moves radially with respect to the casing, one side of each of the O-rings is compressed between the flanges and the radially outer walls of the casing, while the other half of the O-rings are not affected. In this way, the elastomeric O-rings are protected from shear forces which would otherwise tend to destroy them.
By another aspect of the present invention, the central core of the toroidal casing is of the predetermined length such that the O-rings are placed in a preloaded compression so as to establish positive connection between the casing and the plate.
By yet another aspect of the invention, the clearances between the flanges and the central core, and between the flanges and the casing end walls, are controlled to limit the mount deflections in the radial and axial directions, respectively. In the event of a mount overload, the plate flanges will come into contact with the casing and thereby limit further displacement to prevent overloading of the elastomer rings and prevent contact of the mounted part with adjacent objects.
In the drawings as hereinafter described, a preferred embodiment and modified embodiments are depicted; however, various other modifications and alternative constructions can be made thereto without departing from the true spirit and scope of the invention.